18.5 hp OHV Intek only run on choke when hot

[slomo]

The carb has a restriction of adjustment of the mixture and changing it doesn't seem to help much.

As Scrubcadet10 said, that = a dirty carb inside. Clean the carb first.

On the 30 minute deal, look for vacuum leaks around the carb and intake pipes. Spray carb cleaner around carb sealing areas and intake ports/gaskets. Parts heat up and expand causing leaks. Also would take an old spark plug. Gap to 0.25" or 6mm. Check for a good blue spark. Report back with what you have. Check your spark at initial cold startup and at 30 mins.

slomo

 

[Scrubcadet10]

date code appears to 040910Z2 or 3.

 

[Rivets]

This engine has a Nikki carb, superseded to part number 594593.

 

[bob22cn]

It has the Nikki carb. Is it worth rebuilding it or buying a new Walbro?

Amazon has new replacement carbs for like $20.

Jack's Small Engines has rebuild kit for like $50. Any thoughts on rebuild vs new?

 

[slomo]

It has the Nikki carb. Is it worth rebuilding it or buying a new Walbro?

Amazon has new replacement carbs for like $20.

Jack's Small Engines has rebuild kit for like $50. Any thoughts on rebuild vs new?

Amazon carbs are risky. They are NOT guaranteed to work 100% like OEM Briggs carbs. Some Chinese Gambler Series carbs do work.

So you dump 20 bucks on a Chinese and it doesn't work. Then have to shell out 50 smackers for a rebuild kit. Not saving any money if the Chinese carb is junk.

Last Chinese carb I installed needed machining. It was on a Briggs 3.5hp horizontal with a pulsa-jet carb. The fuel pump spring area in the carb body was too small. Needed opening up with a file and sandpaper so the fuel pump would work proper. The spring and diaphragm protector ring wouldn't plunge into the carb body deep enough. It does work now I have to say. Think the carbs with some flaws are sold on ebay and amazon at cheap prices.

slomo

 

[slomo]

Clean and or rebuild the OEM Briggs carb. Boil the sucker like Bertsmobile1 said.

slomo

 

[bob22cn]

Thanks guys; will order the rebuild kit and see how it goes.

 

[slomo]

The carb has a restriction of adjustment of the mixture and changing it doesn't seem to help much.

That is a dirty or clogged low speed pilot circuit inside the carb.

slomo

 

[bob22cn]

But why only after getting hot for >15 minutes?

 

[bob22cn]

Used the rebuild kit; carb was really spotless inside. Needle valve a bit worn.
Started right up and idled well; have to see how it behaves later this week after 30 minutes of mowing.
If it gets goofy, I think next step is a new head gasket, not much else to go wrong i don't think.